Wave Induced Loads Research And Application Of Drillship

With the requirements on petroleum and natural gas increasing everyday around theworld, sea resources exploitation expanded to deep sea gradually. Drillship is a special kindof ship with moon pool in the midship, because of its advantageousmobility and largeloading variability，now have already become one of the most important equipment onresources exploited in deep sea. The primary question is the security about structurestrength during lifetime and appropriate determination on wave induced loads which theship structure encountered sometimes has a great effect on the structure design.This papermainly research on the wave induced loads that the aimed ship encountered in order toachieve the load distribute characteristics along the longiludinal direction. The maincontents are as follows:Firstly, according to the hull molded lines, establishing the aimed drillship’s wetsurface model and mass distribution model. Base on the P-M wave spectrum and the NorthAtlantic wave scatter diagram, the Wadam and Postresp module in the SESAM softwaresystem are used to analyse the linear wave induced loads，long-term forecast are carried outof two loading state. The calculated results are compared to the ABS standard. Thedrillship’s wet surface model with no moon pool opening is established. According to theincreased buoyancy because of the canceled moon pool opening，adjust the mass model,assure that the floating state same as the model which have moon pool opening. Long-termforecast are carried out again reusing Wadam and Postresp programs. Analysis the waveinduced load distribution along the ship when the aimed drillship have no moon poolopening.Secondly, executing wave induced loads long-term forecast use the SESAM softwaresystem Wasim module when the aimed drillship have speed under two load state. The speedis selected between0to12knots，increasing by1knot. Getting the wave induced loadsvariation tendency affected by speed. Taking into account the non-linear effects, Long-termforecast about the drillship’s wave induced loads are carried out at zero speed and thedesign speed, The non-linear results is compared to the linear results and analysis thedifferences. Given a series of regular waves in different wave height, simulation of linearand nonlinear wave induced loads at typical cross-sections are calculated in time domain.Then analyse the affects by wave height changes of nonlinear wave induced loads.In the end, establishing the three cabin finite element model around moon pool of theaimed drillship use MSC.patran, boundary constraint is applied according to the ABSspecification, loading conditions is applied according to the loading manual. The Strengthassessment is calculated through MSC.nastran according to the ABS specification based onlinear and nonlinear waves induced loads.